This time last year, we found out that the Forestry Commission England intended to spray bacterial toxin from a helicopter onto oak woodland designated as a Site of Special Scientific Interest. They were trying to eradicate oak processionary moth from the area. This invasive species damages oak trees and produces an irritant that can cause rashes and other medical problems if people come into contact with it. The RSPB joined forces with Butterfly Conservation and others to raise concerns about the impacts of the spraying on the site’s irreplaceable wildlife. We felt that the risks and benefits of this approach had not been properly weighed up, and that – although the Forestry Commission said it was a ‘one off’ – it set a worrying precedent for using aerial pesticide spraying as a pest control method.
The spraying went ahead and, sure enough, one year on we find ourselves in the same situation after more moths were discovered. This time the area to be treated is a small (2.6 hectares) section of a woodland near the original site in West Berkshire. Again, the toxin will be sprayed from a helicopter to target the caterpillars as they feed on the emerging leaves of oak trees.
Oak processionary moth is an invasive non-native species and the RSPB agrees that it needs to be controlled. The moth is native to southern Europe and was introduced accidentally to England in 2006, probably on an imported oak tree. Had the relevant authorities managed to quickly detect and effectively control it when it first arrived – required under the Convention on Biological Diversity, to which the UK is signatory – we would have stood a good chance of eradicating it quickly, cheaply and before the ecological damage was done. As I have written previously (here)- when it comes to tackling non-native invasive species (one of our four horsemen of the ecological apocalypse), prevention is better and cheaper than the cure.
Unfortunately early action didn’t happen.
Maybe, we will all do better next time. UK support for the new EU Regulation on Invasive Species suggests the right intent. Yet, for oak processionary moth, our only option now is to try to limit its spread. Oak processionary moth will not be kept in check by natural predation in the UK and climate change is likely to help it advance.
Six Oaks Wood: ancient (dating from the 1600's) semi-natural woodland at Coombes Valley RSPB reserve. Photo by Andy Hay (rspb-images.com)
Any action we take on controlling non-native species like this moth has to be done strategically and has to make environmental sense. It’s easy to cause more harm than good with poorly thought out action. In this example, attempts to kill the oak processionary moth will also impact on populations of native butterflies, moths and other invertebrates, essential food for birds like the rapidly-disappearing lesser spotted woodpecker and in some cases – as in the case of the purple emperor – rare species in their own right. Although the toxin was chosen to be as specific as possible, it is lethal to all butterfly and moth species. More targeted approaches, such as removing individual moth nests, are available.
There is currently a lot of interest in aerial pesticide spraying to tackle emerging threats to our woodland. Research is even underway to develop aerial spraying of fungicides to tackle ash dieback – disturbing as this could have a catastrophic effect on our native fungi, which are essential for soil creation, nutrient cycling and plant growth.
The pests and diseases threatening our trees are set to get more numerous and widespread as the climate changes. Aerial spraying may be one weapon in the armoury but, like any toxic pest control, it must only be used as a last resort and as part of an integrated approach which focuses on prevention – through much better control of species movements – rapid response to emerging threats, and environmentally responsible control of established species.
All pest control interventions must be based on the best evidence available and action taken must proportionate to the risk. Moreover, their impacts on wildlife must be closely monitored, and the results of this monitoring must inform future decisions on pest management. We need assurances from the Forestry Commission England that aerial spraying isn’t going to become a routine part of pest management in forestry.
The bottom line is that Defra and their counterparts in the devolved administrations need to be prepared to act fast when new problem species arrive.
It is interesting how much interest there is in Oak Processionary moth compared to diseases like Phytopthera ramorum because of which thousands of hectares of larch are being felled - that's because the larch are in the uplands, way, way away and the moths are on the fringes of London and cause direct problems to people.
Either way, this pest is another example of too little, too late and raises fundamental questions about how we deal in future with similar threats - with the best will in the world, the spraying feels much the same as the Levels dredging - 'why doesn't somebody do something ?' - political response, and I've a sneaking suspicion that both FC & EA staff realise that all too well.
This is worrying. The Forestry Commission (FC)does not have a good record on many issues and actions it has taken in the past. If it did then one might have more confidence in this case. While in all probability spraying is needed the FC should already have done a full environmental assessment of the use of the chemical being sprayed and this assessment should be in the public domain. Further, trials should also have been carried out with results fully analysed and also publicly available.
I do hope this is not another of these "knee jerk" reactions approved by DEFRA, when they have known of the problem for some considerable time.
redkite